The present invention relates generally to gas turbine engines, and, more specifically, to fan outlet guide vanes therein.
A turbofan gas turbine engine is typically used for powering an aircraft in flight. A fan is disposed inside a surrounding nacelle and is driven by a core engine for producing thrust to power the aircraft in flight.
Disposed axially downstream from the row of fan blades is a fan outlet guide vane frame or flowpath including a row of outlet guide vanes (OGVs) which deswirl the fan air prior to discharge from the engine. The OGVs extend radially between and are mounted to an outer supporting ring, and an inner supporting ring mounted to the front frame of the core engine forming an OGV frame.
The OGVs are primarily aerodynamic members precisely configured in profile for maximizing aerodynamic efficiency as the fan air is discharged from the engine. The OGVs are typically bolted to the outer and inner rings, and include associated platforms at the opposite span ends thereof for defining the boundaries for the fan air. The platforms may be integral with the OGVs, or may be discrete members mounted therebetween. In both configurations, the platforms create corresponding gaps. Any radial step at the platform gaps due to manufacturing tolerances reduces aerodynamic efficiency.
The number of OGVs is selected for various reasons including aerodynamic performance and attenuation of fan noise during operation. The corresponding airfoils of the OGVs may therefore have relatively high curvature or camber, and may be assembled in a row with high vane count. However, the inner platforms are necessarily disposed at a smaller radius from the engine centerline axis than the outer platforms. For a given number of vanes, the available circumference at the inner platforms is substantially less than that for the outer platforms.
Since the vanes are typically individually assembled between the outer and inner supporting rings, relatively high vane count and relatively high camber makes difficult, if not impossible, assembly of the vanes on low radius ratio fans.
The components of the OGV frame are typically designed for minimizing the overall weight thereof for increasing the efficiency of the engine. The individual OGVs are typically bolted to the supporting rings which affects the vibratory natural frequencies thereof. In order to prevent undesirable aeroelastic flutter and other forms of vibratory stress, the OGVs should have a relatively high natural frequency.
However, the desire to minimize weight requires a relatively thin outer supporting ring, yet a thin ring has less resistance to bending from loads carried thereto by the mounted vanes, and tends to lower the bending natural frequencies of the assembly.
Accordingly, it is desired to provide an improved fan OGV frame for improving aerodynamic efficiency with improved mounting of the vanes in the rings.
A fan outlet guide vane includes integral outer and inner platforms conforming to arcuate sides thereof, and multiple mounting bosses on the platforms. The platform sides are arcuate to conform with the vane sides for improving aerodynamic efficiency. The multiple mounting bosses improve mounting of the vanes to corresponding supporting rings.